Theory and simulation of charge-transfer dynamics at surfaces

Ultrafast charge transfer reactions at surfaces are of importance for many processes in physics, chemistry, and technology. In this project, we study two classes of photoinduced reactions: electron transfer processes at dye-semiconductor interfaces and in molecules adsorbed at metal substrates. These systems are of interest for a fundamental understanding of charge transfer processes at molecular interfaces and relevant for applications in nanocrystalline solar cells and in the new field of molecular electronics. Previous studies have shown that in many of these systems, electron transfer from the molecular adsorbate into the conduction band of the semiconductor or metal substrate occurs on a timescale of only a few femtoseconds.

The key objective of this project is to use theoretical methods to obtain a comprehensive understanding of the different dynamical processes and mechanisms that are of importance in these systems. This includes the influence of insulating/conducting bridge groups, the tuning of the energy of the discrete molecular states with respect to the band structure of the substrate, the effect of surface states, interface effects such as lateral energy transfer processes induced by interaction of adjacent molecules, and the role of electronic dephasing. Furthermore, we plan to study the influence of the laser pulse on the electron dynamics and the possibility to control electron transfer reactions. The theoretical methodology used in these studies is based on a combination of first-principles electronic structure calculations and quantum dynamical simulations. The theoretical studies will be carried out in close collaboration with time-resolved experiments in MAP project C.1.5.